This application relates to and claims priority from Japanese Patent Application No. 11-115274 filed on Apr. 22, 1999, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates generally to filter elements, and particularly to a manufacturing method for a filter element having a corrugated filter portion. The filter element is suitably used for an air cleaner of a vehicle internal combustion engine.
2. Related Art
As shown in FIGS. 11A-11C, JP-A-8-309136 discloses a manufacturing method for a filter element 550 having a corrugated filter portion 510 and a flange portion 520 formed along an outer periphery of the filter portion 510 to protrude outwardly. As shown in FIGS. 11A and 11B, the flange portion 520 is integrally formed with the filter portion 510 by pressing an outer peripheral portion of a corrugated intermediate product 500 having plural ridges 510a of the filter element 550 at a high temperature. After the flange portion 520 is formed, the flange portion 520 is trimmed by cutting away an excess portion 530 of the flange portion 520 disposed outside a broken line xe2x80x9caxe2x80x9d in FIG. 11B along a whole periphery of the flange portion 520. As a result, as shown in FIG. 11C, the filter element 550 is formed. As shown in FIG. 11B, a width of the flange portion 520 including the excess portion 530 in a direction perpendicular to the ridges 510a needs to have a relatively large value such as 330 mm, so that the flange portion 520 has a necessary width in the direction perpendicular to the ridges 510a after trimming.
However, in the above-mentioned method, since the flange portion 520 needs to be trimmed along the whole periphery thereof to have a predetermined dimension, a relatively large amount of material of the filter element 550 is wasted. Further, when the flange portion 520 is trimmed, trimmings of the flange portion 520 may adhere to a surface of the filter portion 510 and worsen a filtering performance of the filter portion 510.
In view of the foregoing problems, it is an object of the present invention to provide a manufacturing method for a filter element in which a less amount of material of the filter element is wasted.
According to the present invention, a filter element having a filter portion and a flange portion formed along an outer periphery of the filter portion to protrude outwardly is manufactured as follows. First, a corrugated intermediate product having a plurality of ridges is formed by folding a filter material. The intermediate product has a first side extending in substantially parallel with the ridges and a second side extending in a direction substantially perpendicular to the ridges. Next, the filter portion and the flange portion are integrally formed respectively from a center portion and an outer peripheral portion of the intermediate product. While the flange portion is formed, the first side of the intermediate product is restricted to a predetermined position corresponding to a shape of the filter element.
As a result, a side of the flange portion extending in parallel with the ridges is formed simultaneously when the flange portion is formed, and does not need to be trimmed after forming. Therefore, a material waste of the filter element is reduced. Further, since the intermediate product is restricted to the predetermined position only at the first side which extends in substantially parallel with the ridges during forming, a non-uniform deformation of a corrugated shape of the filter portion is maintained minimum. As a result, a filtering performance of the filter element is not affected.
Preferably, the filter material includes a first fiber having a first melting point and a second fiber having a second melting point which is lower than the first melting point. The flange portion is formed by pressing the outer peripheral portion of the intermediate product at the second melting point and over.